SIOUX CITY, Iowa -- The DC-10 that crashed in Iowa last summer was so severely damaged by an in-flight engine explosion that landing it safely was virtually impossible, a test pilot told government investigators Tuesday.
The airworthiness of the jetliner was one of the key factors being examined by the National Transportation Safety Board, which convened a hearing to gather facts about the July 19 crash-landing of United Flight 232.
The entire cockpit crew was among the 184 people who survived the spectacular crash at Sioux Gateway Airport when the jet cartwheeled across a runway and plowed into a cornfield, killing 112 passengers.
So far, the probe has centered around a General Electric tail engine that exploded while the Denver-to-Chicago flight was over northwest Iowa.
The disintegration of a large fan blade disk in the engine severed the jet's hydraulic lines, leaving pilots no way to control the aircraft except by engine thrust.
Capt. Al Haynes of Seattle was hailed as a hero for guiding the damaged aircraft to an airport. A flight simulator study discussed at Tuesday's hearing confirmed Haynes' skill.
Some of United Airlines' best pilots and a pilot for the aircraft maker, McDonnell Douglas, tried dozens of simulated landings under the same conditions and could not bring the aircraft down safely, said Phillip Battaglia, a test pilot for DC-10 manufacturer McDonnell Douglas.
'The consensus of the group was that the pilot could fly the airplane but an adequate landing could not be accomplished within the pilots' control,' said John Clark, senior performance engineer for the NTSB.
Clark said the pilots could pick touchdown position, direction or altitude but 'achieving all desired conditions atthe same time were virtually impossible.'
Battaglia said at no time was Flight 232 in stable flight after the engine explosion.
After dozens of simulated landings, Battaglia concluded a safe landing was only possible as a 'random event.'
'The chances of that happening are as unlikely as the chances of this (hydraulic loss) ever happening again,' the test pilot said. Aircraft experts have said the DC-10's hydraulic system, which operates flaps that steer the craft, has built-in redundancies that allow it to function if some lines are cut. But the violent explosion on Flight 232 severed the hydraulic lines at an area near the tail where they converge.
Some of the pilots were able to land the plane on the runway during the simulation but the impact would have destroyed the aircraft, Battaglia said. Even the best landing simulations had the DC-10 speeding off the end of the runway. That type of scenario only would have been safe on a large dry lakebed runway.
NTSB chief accident investigator Robert MacIntosh said the crew could not recall ever having practiced controlling an airplane solely by engine power.
MacIntosh also said there is no procedure published by McDonnell Douglas or any airline flying a DC-10 that specifically addresses total hydraulic loss.
With the jet steadily descending and only able to make right turns, Haynes steered toward Sioux City while United Airlines pilot trainer Dennis Fitch, who happened to be a passenger, manipulated the engine throttles.
With the pilots unable to control airspeed, Flight 232 touched down at 214 knots but the right wing dipped to the ground, causing the jet to cartwheel over the runway, MacIntosh said.
NTSB officials at the outset warned observers no conclusions would be reached at the hearing.
NTSB board member Joseph Nall, the presiding officer at the hearing, also said the inquiry was not being held to determine the liability of the various companies involved.
Published reports over the weekend from a Federal Aviation Administration spokesman suggested a tiny imperfection in the metal disk caused a crack that led to the GE engine explosion.
But United Airlines spokesman Robert Doughty said those reports were extremely premature. He said it normally takes two months to examine engine parts and experts have had only 12 days to look at the disk because of legal entanglements surrounding the accident.